1. Technical Field
The present invention relates to a method of controlling arc welding performed in a manner that, with use of a welding wire as a consumable electrode, a short-circuit period (in which a short circuit is generated between the welding wire and an object to be welded) and an arc period (in which an arc is generated after release of the short circuit) are repeated alternately.
2. Background Art
Conventionally, there have been made some suggestions on decrease in correction processes after arc welding by decreasing spatters generated in arc welding. In one known control method, for example, in an early stage of the arc period after arc regeneration, current is controlled so as to have a current value higher than a current value immediately before the arc regeneration. The current control provides an arc length immediately after arc regeneration with stability and suppresses generation of short circuit, resulting in decrease in spatters (see Japanese Unexamined Patent Application Publication No. 2006-021227, for example).
FIG. 4 shows a waveform of welding current in transitional welding states of a consumable-electrode type arc welding. The horizontal axis shows elapsed time, and the vertical axis shows welding current. In FIG. 4, numeral 101 indicates a short-circuit period where a short circuit occurs between a wire and a base material (i.e., an object to be welded), and numeral 102 indicates an arc period where an arc is generated between the wire and the base material. Numeral 103 indicates an arc regeneration time at which an arc is generated again after short-circuit release. Numeral 104 indicates electric current (in magnitude) immediately before arc regeneration, and numeral 107 indicates electric current (in magnitude) in an early stage of the arc period. Numeral 108 indicates the control time in the early stage of the arc period. Numeral 109 indicates the gradient of increase in welding current from arc-regeneration-before current 104 to early-stage arc current 107.
Increase gradient 109 of welding current is determined to be mild by design. The reason is that steeply increased welding current at arc regeneration wobbles the molten pool and causes unstable movement of a droplet on the tip of the wire. The phenomenon easily causes a feeble short circuit between the wire and the base material, increasing spatters. That is, controlling increase gradient 109 to have mild increase contributes to decrease in spatters.
Besides, early-stage arc current 107 is controlled so as to have a value higher than that of arc-regeneration-before current 104. This allows a droplet to be formed on the tip of the wire in an early stage after arc regeneration, accelerating generation of the next short-circuit and decreasing welding voltage. This further increases welding speed and decreases burn-through in gap welding. Further, the aforementioned current control provides an arc length immediately after arc regeneration with stability and suppresses generation of a short circuit immediately after arc regeneration, resulting in decrease in spatters.